The invention relates to a thermometer comprising a digital display device for displaying the temperature value of the body temperature, which contains a temperature probe with a thermistor as the electric sensing element, and which contains an apparatus electrically and possibly mechanically connected therewith by means of a cable, in which apparatus the digital display device and an electronic circuit are housed, which consists of an interconnection of integrated circuits, transistors, and passive components, which converts the resistance value of the thermistor--which varies as a function of the temperature of the body--into the digital display, and which is fed by a stabilized voltage source.
The thermometer serves the purpose of measuring the body temperature in the case of human beings and animals.
A medical thermometer of this type is known and has been on the market for a long period of time. In the case of this known thermometer, the resistance value produced by a thermistor constructed as a probe (or sensor), is connected into the feedback branch of an operational amplifier, and the constant voltage connected to the other input of this operational amplifier is thus controlled. By this means, a varyingly great voltage occurs, in dependence upon the temperature of the body, at the output of the operational amplifier. This output voltage of the operational amplifier, in cooperation with additional operational amplifiers and a relatively complicated circuit, is brought to the input of an analog-to-digital converter. In additional integrated circuits, which are constructed in the form of separate modules, respectively, this signal is brought to display in connection with a plurality of transistors which are necessarily present. As the display device, an LED- or an LCD-display can be utilized here. Such display devices are sufficiently known per se.
The necessity of a plurality of separate modules within the circuit, and also the utilization of at least five transistors for the display device, inevitably results in that the known apparatus is not only comparatively large in its external dimensions, but that, in addition, due to the outlay required, this apparatus is utilized for reasons of cost only among experts and even in the latter instance, is utilized only to a limited extent.